In some production lines in which an object to be conveyed is worked on and processed while a carrier that supports the object to be conveyed is conveyed, a conveying speed and a conveying pitch (inter-carrier pitch) are differentiated in each of the stages in the production line, depending on the circumstances on a working stage and a processing stage.
Conveyance apparatuses for use in such a production line need to be configured to enable smooth transfer between the stages.
Examples of the conveyance apparatus configured so that a conveying speed for each carrier varies among conveyance areas are described below (e.g., see Patent Literatures 1 to 3).
A conveyance apparatus of Patent Literature 1 is used in a roller conveyor on which an object to be conveyed is conveyed without any carrier. The conveyance apparatus includes: a speed increasing conveyance device that gradually increases the conveying speed and is disposed between roller conveyors; and a speed reducing conveyance device that gradually reduces the conveying speed and is disposed between the roller conveyors. The speed increasing conveyance device is provided at a position where a carrier is transferred from a low-speed roller conveyor to a high-speed roller conveyor, whereas the speed reducing conveyance device is provided at a position where the carrier is transferred from the high-speed roller conveyor to the low-speed roller conveyor, (FIG. 2).
A conveyance apparatus of Patent Literature 2 is provided with a speed adjustment device for increasing or reducing, or adjusting the conveying speed (travelling speed) of a carrier (travelling carriage) moving along a track. In the speed adjustment device, a plurality of speed adjustment units are arranged at a predetermined pitch along a conveyance path, each speed adjustment unit is provided with a speed adjustment pinion to be meshed with a rack of the carrier, and interlocking shafts for interlocking and connecting the plurality of speed adjustment units are provided. In addition, a speed-adjustment rotational drive device which rotationally drives the speed adjustment pinions of the respective speed adjustment units via the interlocking shafts is provided, and a mechanical-type speed change mechanism is interposed at a portion, of each speed adjustment unit, that is located between the interlocking shaft and the speed adjustment pinion.
The speeds of the speed adjustment pinions are different from one another, and the carrier needs to transfer between the speed adjustment pinions having different speeds. In view of the situation, a meshing-adjustment mechanism is provided for accepting rotational deviation of the speed adjustment pinion meshed with the rack of the carrier. The mesh-adjustment mechanism supports the speed adjustment pinion so as to be rotatable by at least one or more pitch angles (FIGS. 3 and 4).
A conveyance apparatus of Patent Literature 3 has a configuration in which pinions arranged at predetermined intervals along a conveyance path are engaged with a rack provided to a carrier (conveyance carriage), and the carrier is moved by rotation of the pinions. In this configuration, the rack is composed of: a body portion having a center portion at which a plurality of fixing rack teeth are provided; and movable portions which are provided at front and rear sides of the body portion and include movable rack teeth. Each movable portion is supported so as to be rotatable around a support shaft portion provided frontward, in the movement direction, of a position at which the movable rack teeth of the movable portion are present (FIGS. 4 to 6).